______ the maths problem is difficult， I'll try very hard to work it out.
A．Though B．When
C．Before D．After
Don't hurry. The bus won't start ______ everybody gets on.
A．since B．as
C．until D．when
I didn't buy the dictionary yesterday _____ my aunt would give me one.
A．until B．because
C．if D．before
We can't do it ______ your help.
A．with B．of
C．under D．without
Japan is ______ the east of China.
A．in B．to
C．on D．at
Sorry, Madam.You’d better come tomorrow because it’s ____ the visiting hours.
A．during B．at
C．beyond D．before
